In conventional, to solve the problem of evaporation of fuel gas in the fuel tank of a car, generally, a fuel gas return channel is added to the fuel tank. Through the negative pressure, the fuel gas returns to the gas inlet end of an internal combustion engine to be used by the engine. Thereby the fuel gas cannot vent outside to cause pollution.
In above mentioned gas return channel, a carbon canister (C/N) is arranged for absorbing evaporated fuel gas. To prevent the drainage of the fuel as the car is tilted, a fuel control valve is added to the gas return tube for closing the gas return tube immediately as the car falls down so that the fuel gas and the fuel will not drain out to cause pollution. Besides, to prevent an over large expansion pressure of the fuel gas in the fuel tank to induce explosion or deformation of the fuel tank, a bypass valve is serially connected to the gas return tube adjacent to the fuel tank. When the fuel tank or the gas return tube is blocked, the valve can be opened for releasing fuel pressure to protect the fuel tank.
Conventionally, the gas return tube connected to the fuel tank and the gas inlet of the engine is formed by using soft tubes to be connected between the fuel control valve and the bypass valve or connected between the fuel control valve, the carbon canister and the bypass valve. However, the longer the soft tubes or the larger number the soft tubes is used, the greater the resistance in the gas return tube is presented, which will reduce the absorption force of negative pressure. Thereby fuel gas cannot be reused smoothly. Furthermore, conventional fuel control valve, carbon canister and bypass valve, etc. have complicated structures so that the manufacturing and assembling processes are time consuming and cost ineffective. The soft tubes may be arranged disordered to occupy a larger space.